Back Contact Solar Cell Electrode Height Differentiation
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Solution Overview
Problem
The alignment accuracy required for connecting finger electrodes using a wiring sheet in back contact solar cells is high, leading to potential short-circuits and reduced carrier collection efficiency due to positional displacement, and increasing the cross-sectional area of finger electrodes to reduce series resistance is limited by stress and warpage concerns.
Innovation Solution
A back contact solar cell design with alternating finger electrodes and bus bar electrodes, where the finger electrodes have non-mounting and wiring-mounting sections with different heights, allowing for easier alignment and reduced series resistance without increasing overall electrode height, and a method for testing solar cells using I-V measurement to ensure defect-free connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the cross-sectional area of finger electrodes is increased to reduce series resistance, then carrier collection efficiency improves, but stress at the electrode-semiconductor interface increases causing warpage and delamination
Solution Approach 1:
The electrode is divided into two regions with different heights: a first region with height H1 for carrier collection and a second region with height H2 (>H1) for wiring connection. This local differentiation allows the electrode to have sufficient cross-sectional area for low resistance in the wiring region while maintaining lower height in the carrier collection region to minimize interface stress and warpage.
2Loss of energy
If wiring sheets are used to connect finger electrodes, then series resistance is reduced, but alignment accuracy requirements increase leading to potential short-circuits
Solution Approach 1:
The invention introduces a height dimension differentiation to solve the alignment problem. By creating a second region with greater height H2, the wiring connection is elevated to a different vertical level, providing a larger target area for wiring sheet connection and reducing sensitivity to horizontal alignment errors, thus decreasing the required alignment accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Facilitates easier alignment and reduced carrier collection loss due to series resistance, improving the conversion characteristics and yield of solar cell modules by allowing for wider positional and angular displacement during wiring assembly, while minimizing stress-related defects.
Implementation Method 1
A general solar cell is a double-sided electrode type solar cell, which includes an electrode on both a light-receiving surface and a back surface. As a solar cell free from a shading loss caused by an electrode, a back contact solar cell has been developed
Implementation Method 2
A back contact solar cell includes a p-type semiconductor layer and an n-type semiconductor layer on the back side. With this structure, excited photocarriers in the semiconductor substrate by incident light from the light-receiving side can be efficiently collected in each conductive semiconductor layer
Data Source
Figure 1~2
Figure 3A~4
Figure 5~6
AI summary
A solar cell (100) includes: a first conductivity-type layer (21) and a second conductivity-type layer (22) each provided on a rear surface of a semiconductor substrate (10); first electrodes (41) provided on the first conductivity-type layer; and second electrodes (42) provided on the second conductivity-type layer. The first electrodes and the second electrodes are spaced apart from each other, and the first electrodes include a plurality of regions isolated from one another by the second electrodes disposed therebetween. Each of the plurality of regions of the first electrodes includes a non-mounting electrode section (410) and a wiring-mounting electrode section (411) having a larger electrode height than the non-connection electrode section. In two adjacent first electrode regions, an imaginary line connecting the top of the wiring-mounting electrode section of one of the regions and the top of the wiring-mounting electrode section of the other region does not cross the second electrode disposed between the two regions.